Experimental Characterization of Frequency-Domain Thermal Impedance for Power Module under Different Boundary Conditions

Frequency-domain thermal impedance model has been proved to be able to predict more complex thermal behaviors of power semiconductor devices under multi-timescales. But the essential prerequisite for accurate thermal prediction is that the key parameters of this model, especially the critical frequencies, are correctly characterized. In this paper, the impacts of potential boundary conditions on the parameters of frequency-domain thermal impedance model are comprehensively investigated through experimental measurements. The testing conditions are set under different levels of power-losses in chip, as well as different cooling environments. The experimental results are analyzed to establish mathematical expressions that reveal the relationship between these conditions and the parameters in frequency-domain thermal impedance model.